It is common for signals to be communicated between integrated circuits on a printed circuit board, or between integrated circuits on multiple printed circuit boards. Signals are transmitted via transmission lines, where the signals may be analog or digital, and the integrated circuits may include microprocessors, microcontrollers, memories, and the like. The transmission lines for carrying the signals may include a bus, a printed circuit board trace, wire, or other type of relatively long metal line.
The conventional transmission of high frequency analog and digital signals may create radio frequency interference (RFI). An intensity of the RFI is related to frequency, duty cycle, amplitude, and edge rates of the transmitted signal. RFI emissions may adversely affect other electronics, such as FM (frequency modulation) radio receivers, and contribute to "crosstalk" on nearby transmission lines.
Shielding, such as coaxial cable has been extensively used to reduce RFI emissions from transmission lines. However, coaxial cable and other shielding methods are typically expensive and may be somewhat unwieldy and difficult to implement effectively.